Tantalum
is one of the most corrosion-resistant materials and has
mechanical properties that are suitable for orthopedic applications.
However, tantalum exhibits bioinert characteristics and cannot promote
the desired level of osseointegration with juxtaposed bone tissues.
To enhance the bioactivity of tantalum, nanoscale surface modifications
via anodization could be a potential approach. In this study, surface
features having nanotubular, nanodimple, and nanocoral morphologies
were fabricated onto tantalum by controlling anodization parameters.
Aside from altering the surface morphology, nanotubular, nanodimple,
and nanocoral feature sizes were precisely fine-tuned between the
20 and 140 nm range. The results indicated that anodized surfaces
consisted of Ta2O5 and non-stoichiometric tantalum
suboxide chemistry. Upon the anodization, surface area of the tantalum
samples increased up to 2-fold, which was accompanied by up to a 3.5-folds
increase in the nanophase surface roughness. Biological studies showed
that anodized tantalum surfaces significantly enhanced protein adsorption
and improved bone cell proliferation and spreading independently of
the anodized surface morphology and feature size. Nanodimple surfaces
having a 90 nm feature size promoted 50% more bone cell proliferation
and 23% more cellular spreading compared to non-anodized tantalum.
Nanodimple surfaces also enhanced alkaline phosphatase activity and
increased Ca mineral deposition up to 5 weeks compared to non-anodized
tantalum, indicating higher bioactivity. In this study, biological
interactions of anodized tantalum surfaces having different morphologies
and feature sizes were examined, for the first time, and the potential
use of nanostructured tantalum was highlighted for orthopedic applications.